Polycarbonate resin, and polycarbonate resin composition

ABSTRACT

Provided is a polycarbonate resin, including, as a raw material, a bisphenol A having 100 ppm by mass or less of isopropenylphenol and 250 ppm by mass or less of 2-(2-hydroxyphenyl)-2-(4-hydroxyphenyl)propane, each detected after heating in air at 175° C. for 1 hour.

TECHNICAL FIELD

The present invention relates to a polycarbonate resin and apolycarbonate resin composition, which are available by selecting andusing a specific raw material, and have a satisfactory hue. Morespecifically, the present invention relates to a polycarbonate resin anda polycarbonate resin composition each having a reduced yellow tint (lowYI value) and an excellent light transmission property.

BACKGROUND ART

A polycarbonate resin (hereinafter sometimes abbreviated as “PC resin”)is excellent in, for example, transparency, mechanical characteristics,thermal stability, electrical properties, and weatherability, and hencehas been used in an optical molded article, such as a light-guidingplate, a lens, or an optical disc, by taking advantage of suchcharacteristics. However, the light transmission property of the resinis lower than that of a polymethyl methacrylate (PMMA) or the like, andhence its color tone has a slightly yellow tint.

Particularly in the case where the light-guiding length of alight-guiding plate using the resin becomes longer, when the materialhas a yellow tint, a light beam having a shorter wavelength is absorbed.Accordingly, there occurs a phenomenon in which a difference in colortone between a portion close to a light source and a portion distanttherefrom is observed, and there occurs a problem in that the color tonebecomes nonuniform. A polycarbonate material having a reduced yellowtint has been required for solving such problem.

With regard to a light-guiding plate or the like, the thinning andupsizing of such product have been progressing. Therefore, there hasbeen a growing requirement for a molding material having highflowability and suppressed in yellowing even in injection molding athigh temperature.

A thin-walled product obtained by injection molding at high temperaturehas heretofore been typically applied to, for example, a digitalversatile disc (DVD). In the application, however, required quality interms of a color tone is not as high as that in a light-guiding memberbecause a required light transmission length is as short as thethickness direction of the disc (about 0.6 mm).

In Patent Document 1, there is a disclosure of a method involvingsetting the total amount of specific eight kinds of impurities in apolycarbonate resin to 750 ppm by mass or less to reduce the number ofwhite spots in an optical disc substrate and an error rate therein.

In Patent Document 2, there is a disclosure of a polycarbonate resincomposition for an optical disc substrate containing a polycarbonateresin produced by using, as a raw material, 2,2-(4-hydroxyphenyl)propane(bisphenol A) in which the content of a cyclic dimer ofp-isopropenylphenol is 150 ppm by mass or less and the content oftrisphenol is 150 ppm by mass or less, and 100 ppm by mass to 500 ppm bymass of a release agent, the resin composition having a feature in thatthe viscosity-average molecular weight of the resin composition in apelletized state is from 10,000 to 17,000, and the hydroxyl groupterminal content thereof is less than 7 mol %. The amount of2-(2-hydroxyphenyl)-2-(4-hydroxyphenyl)propane (2,4-isomer) in thepolycarbonate resin composition is 1,000 ppm by mass or less.

In Patent Document 3, there is a disclosure of a method of producing anaromatic PC including the step of retaining the molten state of thecomposition of bisphenol A and phenol, which is obtained in an apparatusfor producing bisphenol A, under high temperature with an inert gas(nitrogen gas) without granulating the composition, followed by thesupply of the composition to a subsequent PC production apparatus. InPatent Document 3, there is a disclosure that the content of4-isopropenylphenol in the composition of 2,2-(4-hydroxyphenyl)propaneand phenol retained in a molten state to be subjected to thepolymerization of the polycarbonate is 1,000 ppm by mass or less.

CITATION LIST Patent Document

-   [Patent Document 1] JP 4621312 B2-   [Patent Document 2] JP 2001-344813 A-   [Patent Document 3] JP 2002-173530 A

SUMMARY OF THE INVENTION Technical Problem

As disclosed in Patent Documents 1 to 3, various attempts have been madeto obtain a polycarbonate resin having a reduced amount of impuritiesthrough, for example, the improvement of a production method for apolycarbonate resin. However, it is difficult to achieve a low level ofYI value even by those methods. The present invention has been made tosolve such problems, and an object of the present invention is toachieve a low YI value not by paying attention to a method of producingbisphenol A as disclosed in the patent literatures but by using apolycarbonate resin using, as a raw material, a bisphenol A confirmed tosatisfy the criteria of the present invention after part of a lot of thebisphenol A (hereinafter sometimes abbreviated as “BPA”) obtained as araw material has been collected and analyzed for its concentrations ofspecific impurities, and a composition thereof.

Solution to Problem

The inventors of the present invention have found that a polycarbonateresin and a polycarbonate resin composition each having a satisfactoryhue can be produced by using a bisphenol A satisfying the following: theamounts of isopropenylphenol (hereinafter sometimes abbreviated as“IPP”) and a 2,4-isomer detected after the heating of the bisphenol Aobtained as a raw material at 175° C. for 1 hour fall within specificranges.

That is, the present invention includes the following.

1. A polycarbonate resin, including as a raw material, a bisphenol Ahaving 100 ppm by mass or less of isopropenylphenol and 250 ppm by massor less of 2-(2-hydroxyphenyl)-2-(4-hydroxyphenyl)propane, each detectedafter heating in air at 175° C. for 1 hour.

2. The polycarbonate resin according to Item 1, in which the bisphenol Aserving as the raw material satisfies the following formula (i).

(Concentration of isopropenylphenol detected after heating at 175° C.for 1 hour)−(concentration of isopropenylphenol before heating at 175°C. for 1 hour)≦50 ppm by mass   Formula (i)

3. The polycarbonate resin according to Item 1 or 2, wherein thepolycarbonate resin has a viscosity-average molecular weight of from9,000 to 17,500.

4. A polycarbonate resin composition, comprising 100 parts by mass of(A) a polycarbonate resin containing 60 mass % or more of thepolycarbonate resin of any one of Items 1 to 3, and 100 ppm by mass to1,500 ppm by mass of (B) a phosphorus-based antioxidant.

5. The polycarbonate resin composition according to Item 4, wherein (B)the phosphorus-based antioxidant has a pentaerythritol structure.

6. The polycarbonate resin composition according to Item 4 or 5, wherein(B) the phosphorus-based antioxidant comprisesbis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite and/orbis(2,4-dicumylphenyl)pentaerythritol diphosphite.

7. The polycarbonate resin composition according to any one of Items 4to 6, further comprising, with respect to 100 parts by mass of (A) thepolycarbonate resin, 200 ppm by mass to 1,500 ppm by mass of (C) apolyorganosiloxane having a functional group.

8. The polycarbonate resin composition according to Item 7, wherein thefunctional group comprises at least one selected from the groupconsisting of an alkoxy group, an aryloxy group, a polyoxyalkylenegroup, a carboxyl group, a silanol group, an amino group, a mercaptogroup, an epoxy group, and a vinyl group.

9. The polycarbonate resin composition according to Item 7 or 8, whereina difference between a refractive index of (C) the polyorganosiloxaneand a refractive index of (A) the polycarbonate resin is 0.13 or less.

10. A molded body, which is obtained by molding the polycarbonate resincomposition of any one of Items 4 to 9.

11. The molded body according to Item 10, wherein the molded bodycomprises a light-guiding plate.

12. A bisphenol A, having 100 ppm by mass or less of isopropenylphenoland 250 ppm by mass or less of2-(2-hydroxyphenyl)-2-(4-hydroxyphenyl)propane, each detected afterheating in air at 175° C. for 1 hour.

13. A method of producing a polycarbonate resin, including using as araw material, a bisphenol A having 100 ppm by mass or less ofisopropenylphenol and 250 ppm by mass or less of2-(2-hydroxyphenyl)-2-(4-hydroxyphenyl)propane, each detected afterheating in air at 175° C. for 1 hour.

Advantageous Effects of Invention

According to the present invention, there are provided a polycarbonateresin and a composition thereof that can provide a molded body having asatisfactory hue (low YI value).

DESCRIPTION OF EMBODIMENTS <Polycarbonate Resin>

The present invention provides a polycarbonate resin, including as a rawmaterial, a bisphenol A having 100 ppm by mass or less ofisopropenylphenol and 250 ppm by mass or less of2-(2-hydroxyphenyl)-2-(4-hydroxyphenyl)propane (hereinafter abbreviatedas “2,4-isomer”), each detected after heating in air at 175° C. for 1hour.

When the amount of isopropenylphenol is more than 100 ppm by mass, thehue of the polycarbonate resin using the bisphenol A as a raw materialdeteriorates. The amount of isopropenylphenol is preferably 50 ppm bymass or less. Isopropenylphenol is a compound represented by thefollowing general formula (1).

Isopropenylphenol is a substance incorporated as an impurity into theraw material bisphenol A together with, for example, the 2,4-isomer.Isopropenylphenol has been known as a decomposition product of bisphenolA, and has been known as a substance having high reactivity. It has beenknown that when bisphenol A is left to stand in air, bisphenol A changesinto other impurities, such as a cyclic dimer in which twoisopropenylphenol molecules are bonded to each other, and trisphenolproduced by a reaction between bisphenol A and isopropenylphenol. Theinventors of the present invention have found that even when theisopropenylphenol concentration itself of the raw material bisphenol Abefore the production of a polycarbonate is low, concern is raised inthat an impurity produced by the change of isopropenylphenol in thebisphenol A is responsible for an influence on the hue of each of thepolycarbonate resin and a resin composition using the resin.

In view of the foregoing, the inventors have paid attention to the factthat subjecting bisphenol A to a heating test increases itsisopropenylphenol concentration, and hence have found that apolycarbonate resin and a resin composition each having a satisfactoryhue can each be produced by using as a raw material, a bisphenol Ahaving 100 ppm by mass or less of isopropenylphenol and 250 ppm by massor less of 2-(2-hydroxyphenyl)-2-(4-hydroxyphenyl)propane, each detectedafter heating in air at 175° C. for 1 hour.

The 2,4-isomer is an impurity produced as a regioisomer at the time ofthe production of bisphenol A. When the amount of the 2,4-isomer is morethan 250 ppm by mass, the hue of the bisphenol A deteriorates to cause aproblem in terms of the quality of the resin. The amount of the2,4-isomer is preferably 210 ppm by mass or less, more preferably 200ppm by mass or less.

In addition, when the raw material bisphenol A has 50 ppm by mass orless of isopropenylphenol, and 210 ppm by mass or less or 200 ppm bymass or less of the 2,4-isomer, each detected after heating in air at175° C. for 1 hour, a resin and a resin composition each having a moreexcellent hue can be obtained.

As described above, isopropenylphenol in the raw material bisphenol Ahas high reactivity and changes with time, and hence its concentrationreduces with time. After having found that heating the raw materialbisphenol A at 175° C. for 1 hour increases its isopropenylphenolconcentration, the inventors of the present invention have consideredthat the phenomenon may be responsible for a variation in transparencyof each of a polycarbonate resin and a resin composition obtained whenthe obtained bisphenol A is used as it is, and thus have reached theinvention of the present application. When a difference between theisopropenylphenol concentrations before and after the heating test issmall, a resin and a resin composition each having a more excellent huecan be obtained. In the present invention, it is desired that adifference between the concentration of isopropenylphenol detected afterthe heating of the raw material bisphenol A in air at 175° C. for 1 hourand the concentration thereof before the heating (initial value beforethe heating at 175° C. for 1 hour) be preferably 50 ppm by mass or less,more preferably 40 ppm by mass or less, still more preferably 35 ppm bymass or less. In one embodiment of the present invention, a bisphenol Asatisfying the following formula (i) can be used as the raw material.

(Concentration of isopropenylphenol detected after heating at 175° C.for 1 hour)−(concentration of isopropenylphenol before heating at 175°C. for 1 hour)≦50 ppm by mass   Formula (i)

When the raw material bisphenol A in which the difference between theisopropenylphenol concentrations before and after the heating test issmall is used as described above, in addition to a raw material in whichthe amount of isopropenylphenol detected after the heating test fallswithin the range of the present invention be used, a polycarbonate resinand a composition thereof each having a more excellent hue can beobtained.

Of course, when the raw material bisphenol A has 50 ppm by mass or lessof isopropenylphenol, and 210 ppm by mass or less or 200 ppm by mass orless of the 2,4-isomer, each detected after heating in air at 175° C.for 1 hour, and the difference between the concentration ofisopropenylphenol detected after the heating under the conditions andthe concentration thereof before the heating (initial value before theheating at 175° C. for 1 hour) is preferably 50 ppm by mass or less,more preferably 40 ppm by mass or less, still more preferably 35 ppm bymass or less, a polycarbonate resin and a composition thereof eachhaving a more excellent hue can be obtained.

The viscosity-average molecular weight of the polycarbonate resin of thepresent invention is preferably from 9,000 to 17,500, and morepreferably from 11,000 to 15,500. The case where the viscosity-averagemolecular weight of the polycarbonate resin falls within the range ispreferred because of the following reasons: a molding temperaturesuitable for the size of a molded article can be set, and hence themolded article suppresses yellow tint; and a molded body retaining astrength can be obtained.

The viscosity-average molecular weight is a value calculated from theequation [η]=1.23×10⁻⁵Mv^(0.83) by using a limiting viscosity [η]determined through the measurement of the viscosity of a methylenechloride solution at 20° C. with an Ubbelohde-type viscometer.

The content of methylene chloride in the polycarbonate resin of thepresent invention is preferably 200 ppm by mass or less, more preferably50 ppm by mass or less, and still more preferably 20 ppm by mass orless. When the polycarbonate resin is produced by an interfacialcondensation reaction method, methylene chloride having a low boilingpoint is used as an organic solvent. However, it has been known thatunless the methylene chloride is sufficiently removed in aposttreatment, the methylene chloride remains as an impurity in thepolycarbonate resin and hence the yellowing of the resin progresses. Inaddition, the corrosion of a die due to the chloride is liable to occurand the surface of the die is roughened. Accordingly, continuous use ofthe die may reduce the light-guiding property of the molded article.

The polycarbonate resin can be produced by causing the bisphenol Ahaving 100 ppm by mass or less of isopropenylphenol and 250 ppm by massor less of the 2,4-isomer, each detected after heating in air at 175° C.for 1 hour among the bisphenol A obtained as a raw material, to reactwith a carbonate precursor. The reaction is not particularly limited anda known method can be adopted therefor. The reaction is preferablyperformed by an interfacial polymerization method in the presence of anaqueous solution of an alkali compound and a water-insoluble organicsolvent. The reaction can be performed in the presence of apolymerization catalyst as required.

Examples of the alkaline compound include: alkali metal hydroxides, suchas sodium hydroxide and potassium hydroxide; and alkaline earth metalhydroxides, such as magnesium hydroxide and calcium hydroxide. Amongthem, an alkali metal hydroxide is preferred, and sodium hydroxide ismore preferred. The dihydric phenol-based compound is preferably used asa mixture with the alkaline compound aqueous solution.

As the water-insoluble organic solvent, for example, a halogenatedhydrocarbon, such as methylene chloride, chlorobenzene, or chloroform,is preferred, and methylene chloride is more preferred.

Examples of the polymerization catalyst include tertiary amines andquaternary ammonium salts. Examples of the tertiary amine includetrimethylamine, triethylamine, and tripropylamine. Examples of thequaternary ammonium salt include trimethylbenzylammonium chloride andtriethylammonium chloride. As the polymerization catalyst, a tertiaryamine is preferred, and triethylamine is more preferred.

In addition, a molecular weight modifier may be used, as necessary. Themolecular weight modifier is not particularly limited as long as themodifier is a monohydric phenol, and examples thereof include phenol,o-n-butylphenol, m-n-butylphenol, p-n-butylphenol, o-isobutylphenol,m-isobutylphenol, p-isobutylphenol, o-t-butylphenol, m-t-butylphenol,p-t-butylphenol, o-n-pentylphenol, m-n-pentylphenol, p-n-pentylphenol,o-n-hexylphenol, m-n-hexylphenol, p-n-hexylphenol, p-t-octylphenol,o-cyclohexylphenol, m-cyclohexylphenol, p-cyclohexylphenol,o-phenylphenol, m-phenylphenol, p-phenylphenol,o-n-nonylphenol,m-n-nonylphenol, p-n-nonylphenol, o-cumylphenol,m-cumylphenol, p-cumylphenol, o-naphthylphenol, m-naphthylphenol,p-naphthylphenol, 2,5-di-t-butylphenol, 2,4-di-t-butylphenol,3,5-di-t-butylphenol, 2,5-dicumylphenol, 3,5-dicumylphenol,p-cresol, amonoalkylphenol having a linear or branched alkyl group having 12 to 35carbon atoms on average at the ortho-, meta-, or para-position,3-pentadecylphenol, 9-(4-hydroxyphenyl)-9-(4-methoxyphenyl)fluorene,9-(4-hydroxy-3-methylphenyl)-9-(4-methoxy-3-methylphenyl)fluorene, and4-(1-adamantyl)phenol. Among them, p-t-butylphenol, p-cumylphenol, andp-phenylphenol are preferred, and p-t-butylphenol is more preferred.

For example, the following phase-transfer catalyst may be preferablyused as the catalyst: a tertiary amine or a salt thereof, a quaternaryammonium salt, or a quaternary phosphonium salt. Examples of thetertiary amine include triethylamine, tributylamine,N,N-dimethylcyclohexylamine, pyridine, and dimethylaniline. In addition,examples of the tertiary amine salt include hydrochlorides and bromatesof those tertiary amines. Examples of the quaternary ammonium saltinclude trimethylbenzylammonium chloride, triethylbenzylammoniumchloride, tributylbenzylammonium chloride, trioctylmethylammoniumchloride, tetrabutylammonium chloride, and tetrabutylammonium bromide.Examples of the quaternaryphosphonium salt include tetrabutylphosphoniumchloride and tetrabutylphosphonium bromide. Each of those catalysts maybe used alone, or two or more kinds thereof may be used in combination.Among the catalysts, tertiary amines are preferred, and triethylamine isparticularly suitable.

<Polycarbonate Resin Composition> [(A) Polycarbonate Resin]

In another aspect of the present invention, there is provided apolycarbonate resin composition obtained by blending (A) a polycarbonateresin containing the polycarbonate resin of the present invention with(B) a phosphorus-based antioxidant to be described later.

The polycarbonate resin composition of the present invention maycontain, as (A) the polycarbonate resin, a polycarbonate resin exceptthe polycarbonate resin of the present invention to the extent that theresin does not affect the hue, transparency, mechanical characteristics,and the like of the composition. In that case, the ratio of thepolycarbonate resin of the present invention in (A) the polycarbonateresin is preferably 60 mass % or more, more preferably 80 mass % ormore, still more preferably 100 mass %. When two or more ofpolycarbonate resins are used as a mixture, the polycarbonate resins aredesirably used after the viscosity-average molecular weight of theentirety of the polycarbonate resins has been adjusted to fall withinthe above-mentioned range.

[(B) Phosphorus-Based Antioxidant]

In another aspect of the present invention, there can be provided apolycarbonate resin composition obtained by blending 100 parts by massof (A) the polycarbonate resin with 100 ppm by mass to 1,500 ppm bymass, preferably 300 ppm by mass to 1,200 ppm by mass of (B) thephosphorus-based antioxidant. When the amount of the antioxidant is lessthan 100 ppm by mass, an effect as an antioxidant is not sufficient andhence an increase in YI value cannot be suppressed. Meanwhile, when theamount is more than 1,500 ppm by mass, the decomposition of thepolycarbonate may progress owing to an acid generated by thedecomposition of the antioxidant.

For example, the following antioxidant may be used as thephosphorus-based antioxidant: phosphorous acid, phosphonous acid,phosphonic acid, or esters thereof, or a tertiary phosphine. Among them,a phosphorous acid ester having a pentaerythritol structure representedby the following general formula (2) is preferred.

In the general formula (2), R¹ and R² each represent hydrogen, an alkylgroup, a cycloalkyl group, or an aryl group. The cycloalkyl group andthe aryl group may each be substituted by an alkyl group.

When R¹ and R² each represent an aryl group, R¹ and R² each preferablyrepresent an aryl group represented by the following general formula(a), (b), or (c).

[In the formula (a), R³ represents an alkyl group having 1 to 10 carbonatoms.]

[In the formula (b), R⁴ represents an alkyl group having 1 to 10 carbonatoms.]

Specific examples thereof may includebis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphiterepresented by the following formula (3),bis(2,4-dicumylphenyl)pentaerythritoldiphosphite represented by thefollowing formula (4), and compounds represented by the followingformulae (5) to (8).

Bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphiterepresented by the formula (3) [such as ADK STAB PEP-36: manufactured byADEKA Corporation] and/or bis(2,4-dicumylphenyl)pentaerythritoldiphosphite represented by the formula (4) [such as Doverphos S-9228PC:manufactured by Dover Chemical Corporation] is suitable in the presentinvention.

[(C) Polyorganosiloxane Having Functional Group]

In addition, 200 ppm by mass to 1, 500 ppm by mass, more preferably 300ppm by mass to 1,200 ppm by mass of (C) a polyorganosiloxane having afunctional group can be blended into the polycarbonate resin compositionof the present invention, with respect to 100 parts by mass of (A) thepolycarbonate resin. Together with any other component, blending (C) thepolyorganosiloxane having a functional group at a content in the rangeof from 200 ppm by mass to 1,500 ppm by mass can improve thereleasability of the molded article. Further, the blending cansignificantly reduce the occurrence of a silver streak and the amount ofa die deposit even under a high-temperature molding condition largelyexceeding 300° C., especially under a continuous molding condition.

The polyorganosiloxane having a functional group preferably has, as thefunctional group, at least one kind of functional group selected fromthe group consisting of an alkoxy group, an aryloxy group, apolyoxyalkylene group, a carboxyl group, a silanol group, an aminogroup, a mercapto group, an epoxy group, and a vinyl group.

The viscosity of the polyorganosiloxane having a functional group at 25°C. is preferably 10 mm²/sec or more from the viewpoint of itslubricating effect, and is more preferably 200 mm²/sec or less from theviewpoint of its dispersibility in the polycarbonate resin. From theforegoing viewpoints, the viscosity range of the polyorganosiloxanehaving a functional group is still more preferably from 20 mm²/sec to150 mm²/sec, particularly preferably from 40 mm²/sec to 120 mm²/sec.

In order to prevent the transparency of the polycarbonate resincomposition from reducing, a difference between the refractive index ofthe polyorganosiloxane having a functional group and the refractiveindex of the polycarbonate resin is preferably reduced to the extentpossible, for example, to 0.13 or less. The refractive index of thepolyorganosiloxane having a functional group is preferably 1.45 or more,more preferably 1.50 or more, still more preferably 1.52 or more becausethe refractive index of the polycarbonate resin is about 1.58.

[Additive]

Any other resin or an additive, such as an oxidation inhibitor, aweathering agent, a lubricant, a release agent, a plasticizer, aflowability improver, or a antistatic agent, can be added to thepolycarbonate resin composition of the present invention at the time ofits mixing or at the time of its molding to the extent that its physicalproperties are not impaired.

[Method of Producing Polycarbonate Resin Composition]

A method of producing the polycarbonate resin composition of the presentinvention is, for example, a method involving melting and kneading therespective components by a conventionally known method.

For example, the following method is appropriately selected: therespective components are dispersed and mixed with a high-speed mixer,typified by a Tumbling mixer, a Henschel mixer, a ribbon blender, or asuper mixer, and then the resultant is melted and kneaded with anextruder, a Banbury mixer, a roll, or the like.

The polycarbonate resin composition of the present invention can besuitably used in molding at high temperature exceeding 300° C. forproducing a thin-walled molded article, and a molded article to beobtained has a low YI value. The polycarbonate resin composition of thepresent invention containing the polycarbonate resin using as a rawmaterial, the bisphenol A having 100 ppm by mass or less ofisopropenylphenol and 250 ppm by mass or less of2-(2-hydroxyphenyl)-2-(4-hydroxyphenyl)propane, each detected afterheating in air at 175 ° C. for 1 hour, can achieve a ΔYI representing achange in hue of a molded body of preferably 0.15 or less, morepreferably 0.14 or less even when a molding time in, for example,high-temperature molding at 360° C. is extended from 30 seconds to 600seconds. The foregoing means that even in long-term high-temperaturemolding, a molded article to be obtained is excellent in hue.

A molding method involving using the polycarbonate resin composition ofthe present invention is not particularly limited, and a molding methodsuch as injection molding, injection compression molding, extrusionmolding, or blow molding can be applied.

A molded article obtained by molding the polycarbonate resin compositionof the present invention has a low YI value and is excellent in hue.Accordingly, the molded article can also be suitably used in alight-guiding member, such as a light-guiding plate having a longlight-guiding length in which a required light transmission length isnot the thickness direction of a thin-walled molded body but thelongitudinal direction of a planar molded body. The molded body obtainedby molding the polycarbonate resin composition of the present inventionis preferably a light-guiding member, more preferably a light-guidingplate.

EXAMPLES

The present invention is described more specifically below by way ofExamples. However, the present invention is by no means limited by theseexamples. Respective components, and measurement methods (calculationmethods) for physical property values and the like used in Examples areas described below.

-   (B) Phosphorus-based Antioxidant-   (B-1) ADK STAB PEP-36-   [bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite,    manufactured by ADEKA Corporation]-   (B-2) Doverphos S-9228PC [bis(2,4-dicumylphenyl)pentaerythritol    diphosphite, manufactured by Dover Chemical Corporation]-   (C) Polyorganosiloxane having Functional Group KR-511 [manufactured    by Shin-Etsu Chemical Co., Ltd., polyorganosiloxane having a methoxy    group], refractive index: 1.52, viscosity: 25° C., 85.8 mm²/sec

(1) Measurement of YI Value

A YI value was measured with a spectrophotometer “U-4100” (manufacturedby Hitachi High-Technologies Corporation) under the conditions ofilluminant C and 2-degree field of observer angle.

(2) Method of Measuring Viscosity-Average Molecular Weight

The limiting viscosity [η] of a methylene chloride solution at 20° C.was measured with an Ubbelohde-type viscosity tube, and aviscosity-average molecular weight was calculated from the followingrelational expression (Schnell's equation).

[η]=1.23×10⁻⁵ ×Mv ^(0.83)

Example 1

An obtained bisphenol A (initial IPP concentration: 5 ppm by mass,initial 2,4-isomer concentration: 102 ppm by mass) was heated under thefollowing conditions. That is, 10 g of the bisphenol A was loaded into acolorimetric tube having a diameter of 30 mm to be used in themeasurement of an APHA or the like, and was heated in an electricfurnace at 175° C. After the heating for 1 hour, the colorimetric tubewas removed from the electric furnace and cooled. After that, thesolidified bisphenol A was removed and subjected to impurity analysis.The bisphenol A was analyzed for the concentration of isopropenylphenol(hereinafter sometimes abbreviated as “IPP”) and the concentration ofthe 2,4-isomer by high performance liquid chromatography. A highperformance liquid chromatograph (manufactured by Waters, model: 2695,column: manufactured by GL Sciences Inc., Inertsil (trademark) ODS-3V)was used in the analysis including the analysis of the initialconcentration. The mobile phase which was 25 mass % aqueous solution ofacetonitrile kept for 45 minutes, and then analysis mode changed to 3.5mass %/min gradient mode. After having reached 100 mass % acetonitrile,this condition was retained for 5 minutes. The injection amount of thesample was set to 5.0 μL, a column temperature was set to 40° C., a flowrate was set to 1.0 mL/min, and an analysis wavelength was set to 277nm.

As a result of the HPLC measurement, it is found that the IPPconcentration was 37 ppm by mass and the 2,4-isomer concentration was103 ppm by mass, each after the heating test. The results are shown inTable 1-1. A polycarbonate resin was produced by using a bisphenol A ofthe same lot as that of the bisphenol A as a raw material in accordancewith the following production example.

Production Example: Production of Bisphenol A Polycarbonate Resin (1)Polycarbonate Oligomer Synthesis Step

To 5.6 mass % aqueous sodium hydroxide, sodium dithionite was added inan amount of 2,000 ppm by mass relative to bisphenol A (hereinaftersometimes abbreviated as “BPA”) to be dissolved later, and BPA obtainedin this example was then dissolved therein so that the concentration ofBPA became 13.5 mass %, to thereby prepare a solution of BPA in aqueoussodium hydroxide. The solution of BPA in aqueous sodium hydroxide,methylene chloride, and phosgene were continuously passed through atubular reactor having an inner diameter of 6 mm and a tube length of 30m at flow rates of 40 L/hr, 15 L/hr, and 4.0 kg/hr, respectively. Thetubular reactor had a jacket portion, and cooling water was passedthrough the jacket to keep the reaction liquid at a temperature of 40°C. or less.

The reaction liquid that had exited the tubular reactor was continuouslyintroduced into a baffled tank-type reactor having an internal volume of40 L and provided with a sweptback blade, and then, 2.8 L/hr of thesolution of BPA in aqueous sodium hydroxide, 0.07 L/hr of 25 mass %aqueous sodium hydroxide, 17 L/hr of water, and 0.64 L/hr of a 1 mass %triethylamine aqueous solution were further added to the reactor toperform a reaction.

The reaction liquid overflown from the tank-type reactor wascontinuously taken out and left to stand still to separate and remove anaqueous phase, and a methylene chloride phase was then collected. Theconcentration of the obtained polycarbonate oligomer was 325 g/L, andthe concentration of a chloroformate group thereof was 0.77 mol/L.

(2) Polycarbonate Polymerization Step

After the temperature of the cooling solvent of a 50-liter tank-typereactor provided with a baffle board, a paddle-type stirring blade, anda cooling jacket had become 20° C. or less, 15 L of the oligomersolution, 8.9 L of methylene chloride, 192 g of p-tert-butylphenol, 0.7mL of triethylamine, and a solution of BPA in aqueous sodium hydroxide(obtained by dissolving 1,185 g of BPA in an aqueous solution obtainedby dissolving 647 g of NaOH and 2,000 ppm by mass of sodium dithionitewith respect to BPA to be dissolved later in 9.5 L of water) were addedto perform a polymerization reaction for 30 minutes. After that, 0.8 mLof triethylamine was added to the resultant and the mixture was furtherstirred for 30 minutes.

15 Liters of methylene chloride was added to the mixture for dilution,and then the diluted mixture was separated into an organic phasecontaining a polycarbonate resin, and an aqueous phase containing excessBPA and NaOH, followed by the isolation of the organic phase. Theresultant solution of the polycarbonate resin in methylene chloride wassequentially washed with 15 vol % each of 0.03 mol/L aqueous NaOH and0.2 mol/L hydrochloric acid with respect to the solution. Next, washingwith pure water was repeated until an electric conductivity in theaqueous phase after the washing became 0.05 μS/m or less. A solution ofthe polycarbonate resin in dichloromethane obtained by the washing wasconcentrated and pulverized, and the resultant flake was dried underreduced pressure at 100° C. to provide (A) a polycarbonate resin flake.The viscosity-average molecular weight of the flake is shown in Table 1.The refractive index of the polycarbonate resin obtained in each ofExample 1 and Examples 2 to 6 to be described later was 1.58.

100 Parts by mass of (A) the polycarbonate resin flake thus obtained wasdry-blended with 600 ppm by mass of (B-1) the phosphorus-basedantioxidant and 500 ppm by mass of (C) the polyorganosiloxane having afunctional group, and then the blend was melted and kneaded with asingle screw extruder at a cylinder temperature of 260° C. The resultantstrand was passed through a water tank to be cooled, and was thenpelletized to prepare a polycarbonate resin composition. The resinpellet was dried at 110° C. for 5 hours, and then a flat plate-shapedmolded body measuring 25 mm by 35 mm by 3.0 mm thick was produced fromthe pellet with an injection molding machine “Toshiba EC40N”(manufactured by Toshiba Machine Co., Ltd., clamping force: 40 tons)under each of the following conditions: (i) a cylinder temperaturesetting of 360° C., a die temperature of 80° C., and a cycle time of 30seconds; and (ii) a cylinder temperature setting of 360° C., a dietemperature of 80° C., and a cycle time of 600 seconds.

The YI values of the molded bodies obtained under the respective moldingconditions (i) and (ii) were measured. The results are shown in Table2-1.

Example 2

A bisphenol A having an initial IPP concentration of 6 ppm by mass andan initial 2,4-isomer concentration of 204 ppm by mass was subjected toa heating test in the same manner as in Example 1. Its IPP concentrationand 2,4-isomer concentration after the heating test were 32 ppm by massand 206 ppm by mass, respectively. The results are shown in Table 1-1.

100 Parts by mass of (A) a polycarbonate resin produced by using abisphenol A of the same lot as that of the bisphenol A as a raw materialin the same manner as in Example 1 was dry-blended with (B-1) thephosphorus-based antioxidant and (C) the polyorganosiloxane having afunctional group at ratios shown in Table 2-1, and then a polycarbonateresin composition was prepared in the same manner as in Example 1.Molded bodies were produced from the composition, and their YI valueswere measured. The results are shown in Table 2-1.

Example 3

A bisphenol A having an initial IPP concentration of 4 ppm by mass andan initial 2,4-isomer concentration of 56 ppm by mass was subjected to aheating test in the same manner as in Example 1. Its IPP concentrationand 2,4-isomer concentration after the heating test were 39 ppm by massand 56 ppm by mass, respectively. The results are shown in Table 1-1.

100 Parts by mass of (A) a polycarbonate resin produced by using abisphenol A of the same lot as that of the bisphenol A as a raw materialin the same manner as in Example 1 was dry-blended with (B-1) thephosphorus-based antioxidant and (C) the polyorganosiloxane having afunctional group at ratios shown in Table 2-1, and then a polycarbonateresin composition was prepared in the same manner as in Example 1.Molded bodies were produced from the composition, and their YI valueswere measured. The results are shown in Table 2-1.

Example 4

A bisphenol A having an initial IPP concentration of 12 ppm by mass andan initial 2,4-isomer concentration of 103 ppm by mass was subjected toa heating test in the same manner as in Example 1. Its IPP concentrationand 2,4-isomer concentration after the heating test were 39 ppm by massand 103 ppm by mass, respectively. The results are shown in Table 1-1.

100 Parts by mass of (A) a polycarbonate resin produced by using abisphenol A of the same lot as that of the bisphenol A as a raw materialin the same manner as in Example 1 was dry-blended with (B-2) thephosphorus-based antioxidant and (C) the polyorganosiloxane having afunctional group at ratios shown in Table 2-1, and then a polycarbonateresin composition was prepared in the same manner as in Example 1.Molded bodies were produced from the composition, and their YI valueswere measured. The results are shown in Table 2-1.

Example 5

A bisphenol A having an initial IPP concentration of 6 ppm by mass andan initial 2,4-isomer concentration of 142 ppm by mass was subjected toa heating test in the same manner as in Example 1. Its IPP concentrationand 2,4-isomer concentration after the heating test were 35 ppm by massand 147 ppm by mass, respectively. The results are shown in Table 1-1.

100 Parts by mass of (A) a polycarbonate resin produced by using abisphenol A of the same lot as that of the bisphenol A as a raw materialin the same manner as in Example 1 was dry-blended with (B-2) thephosphorus-based antioxidant and (C) the polyorganosiloxane having afunctional group at ratios shown in Table 2-1, and then a polycarbonateresin composition was prepared in the same manner as in Example 1.Molded bodies were produced from the composition, and their YI valueswere measured. The results are shown in Table 2-1.

Example 6

A bisphenol A having an initial IPP concentration of 19 ppm by mass andan initial 2,4-isomer concentration of 208 ppm by mass was subjected toa heating test in the same manner as in Example 1. Its IPP concentrationand 2,4-isomer concentration after the heating test were 68 ppm by massand 211 ppm by mass, respectively. The results are shown in Table 1-1.

100 Parts by mass of (A) a polycarbonate resin produced by using abisphenol A of the same lot as that of the bisphenol A as a raw materialin the same manner as in Example 1 except that the amount ofp-tert-butylphenol was changed to 147 g was dry-blended with (B-2) thephosphorus-based antioxidant and (C) the polyorganosiloxane having afunctional group at ratios shown in Table 2-1, and then a polycarbonateresin composition was prepared in the same manner as in Example 1.Molded bodies were produced from the composition, and their YI valueswere measured. The results are shown in Table 2-1.

Comparative Example 1

A bisphenol A having an initial IPP concentration of 28 ppm by mass andan initial 2,4-isomer concentration of 285 ppm by mass was subjected toa heating test in the same manner as in Example 1. Its IPP concentrationand 2,4-isomer concentration after the heating test were 30 ppm by massand 289 ppm by mass, respectively. The results are shown in Table 1-2.

100 Parts by mass of (A) a polycarbonate resin produced by using abisphenol A of the same lot as that of the bisphenol A as a raw materialin the same manner as in Example 1 was dry-blended with (B-1) thephosphorus-based antioxidant and (C) the polyorganosiloxane having afunctional group at ratios shown in Table 2-2, and then a polycarbonateresin composition was prepared in the same manner as in Example 1.Molded bodies were produced from the composition, and their YI valueswere measured. The results are shown in Table 2-2.

Comparative Example 2

A bisphenol A having an initial IPP concentration of 245 ppm by mass andan initial 2,4-isomer concentration of 142 ppm by mass was subjected toa heating test in the same manner as in Example 1. Its IPP concentrationand 2,4-isomer concentration after the heating test were 327 ppm by massand 143 ppm by mass, respectively. The results are shown in Table 1-2.

100 Parts by mass of (A) a polycarbonate resin produced by using abisphenol A of the same lot as that of the bisphenol A as a raw materialin the same manner as in Example 1 was dry-blended with (B-1) thephosphorus-based antioxidant and (C) the polyorganosiloxane having afunctional group at ratios shown in Table 2-2, and then a polycarbonateresin composition was prepared in the same manner as in Example 1.Molded bodies were produced from the composition, and their YI valueswere measured. The results are shown in Table 2-2.

TABLE 1-1 Results of heating test of raw material bisphenol A ExampleExample Example Example Example Example 1 2 3 4 5 6 IPP ppm by Initial 56 4 12 6 19 mass 1 Hour 37 32 39 39 35 68 after heating 2,4-Isomer ppmby Initial 102 204 56 103 142 208 mass 1 Hour 103 206 56 103 147 211after heating

TABLE 1-2 Results of heating test of raw material bisphenol AComparative Comparative Example 1 Example 2 IPP ppm by mass Initial 28245 1 Hour after 30 327 heating 2,4-Isomer ppm by mass Initial 285 142 1Hour after 289 143 heating

TABLE 2-1 Example Example Example Example Example Example 1 2 3 4 5 6(A) PC resin parts by mass 100 100 100 100 100 100 (B-1)Phosphorus-based antioxidant ppm by mass 600 1,200 300 (B-2)Phosphorus-based antioxidant ppm by mass 600 600 1,000 (C)Polyorganosiloxane ppm by mass 500 1,000 500 300 500 500Viscosity-average molecular weight ppm by mass 14,800 14,700 15,20014,900 15,100 16,800 Molded body YI (measuring 25 mm  30 seconds @ 1.111.17 1.20 1.18 1.15 1.18 by 35 mm by 3.0 mm thick) 360° C. Molded bodyYI (measuring 25 mm 600 seconds @ 1.25 1.20 1.31 1.27 1.23 1.33 by 35 mmby 3.0 mm thick) 360° C. ΔYI 0.14 0.03 0.11 0.09 0.08 0.15

TABLE 2-2 Comparative Comparative Example 1 Example 2 (A) PC resin partsby mass 100 100 (B-1) Phosphorus-based ppm by mass 600 600 antioxidant(B-2) Phosphorus-based ppm by mass antioxidant (C) Polyorganosiloxaneppm by mass 500 500 Viscosity-average ppm by mass 14,900 14,900molecular weight Molded body YI 30 seconds @ 1.31 1.32 (measuring 25 mmby 360° C. 35 mm by 3.0 mm thick) Molded body YI 600 seconds @ 1.48 1.61(measuring 25 mm by 360° C. 35 mm by 3.0 mm thick) ΔYI 0.17 0.29

Comparison between Examples 1 to 6, and Comparative Examples 1 and 2 ofTables 1-1 and 1-2 shows the following. It is found that the ΔYI valueof the molded body of the polycarbonate resin composition produced byusing the bisphenol A of the present invention having 100 ppm by mass orless of isopropenylphenol and 250 ppm by mass or less of the 2,4-isomer,each detected after heating in air at 175° C. for 1 hour, is 0.15 orless, and hence the molded body maintains a satisfactory hue even when amolding time lengthens. Meanwhile, it is found from their YI values thatthe molded bodies of the polycarbonate resin compositions produced byusing the bisphenol A of Comparative Example 1 in which the amount ofthe 2,4-isomer detected after the heating test at 175° C. for 1 hour ismore than 250 ppm by mass and the bisphenol A of Comparative Example 2in which the amount of isopropenylphenol is more than 100 ppm by masscannot each obtain a satisfactory hue.

INDUSTRIAL APPLICABILITY

According to the present invention, there are provided a polycarbonateresin and a polycarbonate resin composition that can provide a moldedbody having a satisfactory hue (low YI value). The polycarbonate resincomposition can be suitably used as a light-guiding member.

1. A polycarbonate resin, comprising as a raw material, a bisphenol Ahaving 100 ppm by mass or less of isopropenylphenol and 250 ppm by massor less of 2-(2-hydroxyphenyl)-2-(4-hydroxyphenyl) propane, eachdetected after heating in air at 175° C. for 1 hour.
 2. Thepolycarbonate resin according to claim 1, wherein the bisphenol Aserving as the raw material satisfies the following formula (i).(Concentration of isopropenylphenol detected after heating at 175° C.for 1 hour)−(concentration of isopropenylphenol before heating at 175°C. for 1 hour)≦50 ppm by mass   Formula (i)
 3. The polycarbonate resinaccording to claim 1, wherein the polycarbonate resin has aviscosity-average molecular weight of from 9,000 to 17,500.
 4. Apolycarbonate resin composition, comprising 100 parts by mass of (A) apolycarbonate resin containing 60 mass % or more of the polycarbonateresin of claim 1, and 100 ppm by mass to 1,500 ppm by mass of (B) aphosphorus-based antioxidant.
 5. The polycarbonate resin compositionaccording to claim 4, wherein (B) the phosphorus-based antioxidant has apentaerythritol structure.
 6. The polycarbonate resin compositionaccording to claim 4, wherein (B) the phosphorus-based antioxidantcomprises bis(2,6-di-tent-butyl-4-methylphenyl)pentaerythritoldiphosphite and/or bis(2,4-dicumylphenyl)pentaerythritol diphosphite. 7.The polycarbonate resin composition according to claim 4, furthercomprising, with respect to 100 parts by mass of (A) the polycarbonateresin, 200 ppm by mass to 1,500 ppm by mass of (C) a polyorganosiloxanehaving a functional group.
 8. The polycarbonate resin compositionaccording to claim 7, wherein the functional group comprises at leastone selected from the group consisting of an alkoxy group, an aryloxygroup, a polyoxyalkylene group, a carboxyl group, a silanol group, anamino group, a mercapto group, an epoxy group, and a vinyl group.
 9. Thepolycarbonate resin composition according to claim 7, wherein adifference between a refractive index of (C) the polyorganosiloxane anda refractive index of (A) the polycarbonate resin is 0.13 or less.
 10. Amolded body, which is obtained by molding the polycarbonate resincomposition of claim
 4. 11. The molded body according to claim 10,wherein the molded body comprises a light-guiding plate.
 12. A bisphenolA, having 100 ppm by mass or less of isopropenylphenol and 250 ppm bymass or less of 2-(2-hydroxyphenyl)-2-(4-hydroxyphenyl)propane, eachdetected after heating in air at 175° C. for 1 hour.
 13. A method ofproducing a polycarbonate resin, comprising using as a raw material, abisphenol A having 100 ppm by mass or less of isopropenylphenol and 250ppm by mass or less of 2-(2-hydroxyphenyl)-2-(4-hydroxyphenyl)propane,each detected after heating in air at 175° C. for 1 hour.